Leap Year & Season Dates Calculator
Check whether a year is a leap year, and find the dates of the March and September equinoxes and June and December solstices — the astronomical start of each season.
How to use
- 1Enter a year.
- 2See whether it's a leap year and the equinox and solstice dates (UTC).
How it's calculated
Leap year: divisible by 4, except centuries unless divisible by 400. Equinoxes and solstices: Meeus's astronomical algorithm (mean values, accurate to within about an hour for 2000–3000).
Frequently asked questions
Why is 1900 not a leap year but 2000 is?
Century years are leap years only if divisible by 400, keeping the calendar aligned with the solar year of about 365.2422 days.
When does spring start?
Astronomically at the March equinox (around 20 March) in the Northern Hemisphere; meteorologists use 1 March.
Why might the date differ in my time zone?
Dates are shown in UTC; in the Americas an equinox late on the 20th UTC can fall on the 19th or 20th locally.